This invention relates to a continuously variable transmission and more particularly to a continuously variable transmission in which primarily inertial reactions on a suitably arranged mass distribution are employed as coupling forces and torques to enable net transfer of energy from an input to an output. The time integral of the output torque and, if applicable, the input torque resulting from these inertial reactions is balanced by the time integral of a reaction torque resulting from these inertial reactions. The reaction torque is applied to the fixed surrounding or the transmission housing or otherwise so as to enable the transmission process to take place in a cyclic manner. In some cases during the cyclic movements of the transmission mechanisms, forces and moments other than the aforesaid inertial reactions may be additionally or otherwise employed to cause transfer of energy from the input to the output of the transmission. Even those cyclic movements of the transmission mechanisms themselves required to cause transfer of energy from the input to the output by other than the aforesaid inertial reactions, may be caused or assisted by means other than inertial reactions.
Transmissions which have fixed input/output speed ratios are not suitable for a wide variety of operating conditions. In order to match the input/output variables, namely the torque and speed, so that transmission losses are reduced and to allow optimum operating conditions at the input/output and to avoid excessive stresses developing in the transmission under transient conditions at the input/output, variable transmissions are necessary.
Using discretely variable transmissions, the speed ratio is changed in a finite number of steps. The above said benefits of a variable transmission are achieved only partially by this method.
Further, the number of steps are limited by economic and practical reasons.
A variety of continuously variable transmissions are known. In the main they use frictional elements, hydraulic elements (motor or turbine/pump) or electro-magnetic elements (motor/generator) to transmit power. With the exception of electro-magnetic methods, these transmissions are inefficient due to slip under transient conditions of acceleration and deceleration due to limited response capacity, especially under rapidly changing input/output conditions. Electro-magnetic systems to avoid such inefficiencies can be very costly and not practical under many circumstances due to space and weight conditions.
The applicant is aware of a number of prior proposals which endeavour to utilize gyroscopic rotors to achieve continuously variable transmission.
The device disclosed in U.S. Pat. No. 4,169,391 relied on varying the moment of inertia of the rotors by hydraulic means to generate a net output torque and to match the input/output conditions. This is extremely difficult to achieve especially under rapidly varying input/output conditions. Furthermore, the hydraulic system described is complex.
The device disclosed in the U.S. Pat. No. 3,851,545 on the other hand relied on maintaining appropriate spin orientations by external power input. This adds significant complexity to the invention disclosed especially under rapidly varying input/output conditions.
The applicant under the International Application PCT/NZ92/00004, disclosed a device based on gyroscopic rotors. This device relied on pumping action by Coulomb damped oscillation (xe2x80x9cvibrationxe2x80x9d) of the gyroscopic rotors about the spin axis. A hydraulic system capable of a fraction of the total power transmission was required to cause the vibration and the xe2x80x9cvibrationxe2x80x9d is unpredictable under high damping ratios. Further, spring elements are required to cause the xe2x80x9cvibrationxe2x80x9d and hence hysteresis losses. An additional speed controller device was required to achieve a useful operating range.
The applicant is also aware of another proposal in which a gyroscopic rotor is mounted on the inner frame of a gimbal support and the outer frame of the gimbal is oscillated to cause gyroscopic torque alternating in direction. Here again with a spring system, the proposal was to cause effectively a coulomb damped vibration and from this vibration, the total power transmission was to have occurred either through hydraulic means or through an equivalent of a complex coulomb damping that would result from the resistance at the output through one-way clutches. The unpredictability of the proposed oscillation in this system is thus very high and the spring system will result in greater hysteresis losses since total power transmitted resulted directly from the xe2x80x9cvibrationxe2x80x9d. Further, only small amplitudes of oscillation were allowed, thus requiring high forces to cause a given power transmission.
Accordingly, it is an object of the present invention to provide a continuously variable transmission in which such disadvantages are reduced.
In accordance with the present invention there is provided a transmission comprising a fixed housing or support, input means moveable relative to said support, a torque shaft rotatable about its longitudinal axis, a driven shaft arranged to be rotated about its longitudinal axis by the torque shaft, a first one way clutch between the torque shaft and driven shaft, linkage means rotatable about the axis of rotation of the driven shaft under the influence of said input means and an inertial body mounted on the linkage means to be cyclically angularly deflected in response to the input means, the reaction forces generated by the inertial body as it is cyclically deflected being applied to the torque shaft as positive and negative torque and the torque shaft being connected over a second one-way clutch opposite to the first one-way clutch either to said support or to the driven shaft over a rotation reversal system whereby the driven shaft can be rotated by the torque shaft in one sense of rotation only.
The inertial body preferably comprises a rotor.
In one embodiment of the invention the linkage may comprise an outer frame rotatable about a first frame axis and an inner frame rotatable relative to the outer frame about a frame axis perpendicular to the first frame axis, the inner frame carrying said inertial body. The outer frame may be fixed to the input means for rotation therewith. The inertial body may be a rotor rotating about an axis orthogonal to the second frame axis. The torque shaft may be connected by gearing to the inner frame such that torque applied by the inertial body to the inner frame, when deflected by rotation of the inner frame, will be transmitted to the torque shaft.
In another embodiment of the invention the input means may comprise a drive shaft reciprocable along an axis generally coincident with or parallel to that of the output shaft, the inertial body being arranged on the linkage means so as to be angularly deflected in a plane containing or parallel with the axis of the driven shaft as the drive shaft reciprocates. The linkage may be an elbow linkage pivotally connected at one end to the drive shaft and at its other end being immovable relative to the driven shaft along the axis of the latter, the inertial body being mounted on one arm of the elbow linkage so as to be angularly deflected as the drive shaft reciprocates. The linkage may comprise a gimbal the outer frame of which is fixed relative to the torque shaft and rotatable relative to the drive shaft, the inertial body being mounted on the inner frame of the gimbal and means being provided to rotate the inner frame of the gimbal in response to reciprocation of the drive shaft. The inner frame may be connected to the drive shaft so as to be oscillated as the drive shaft reciprocates. The connection between the drive shaft and the inner frame may be connecting rod means or rack-and-pinion means. In this arrangement if the inertial body is a rotor, means may be provided between the inner frame and the rotor whereby the input also causes rotation of the rotor.
Means may be provided whereby the speed of rotation of the rotor can be varied relative to the input.
Two meshing gears may be interposed between the first one-way clutch and the driven shaft and three meshing gears may be interposed between the second one-way clutch and the driven shaft such that whichever clutch is not free-wheeling will drive the driven shaft in the same sense of rotation.
The input means may be additionally coupled to the output means via a third one way clutch such that the input means is driven by the output means when the speed of the latter exceeds that of the input means, in all other conditions the third one way clutch freewheeling. The third one way clutch may be coupled to the input means via a variable ratio gear system.
In yet another embodiment of this invention the output means may be a body rotatable about a fixed support, the input means may be a drive shaft reciprocable toward and away from said fixed support, the linkage may comprise an elbow linkage pivotally connected at one end to the drive shaft and at its other end to a frame rotatable with said body and the torque shaft may be connected over said first one-way clutch with said support and over said second one-way clutch with the frame.